How to add usermeta for existing users when user profile is updated

Question

I need to add an usermeta field for users when they decide to modify some account informations on a custom form. At the moment I'm calling the wp_update_user() but since I want that the modifications are approved first, I want to add a field into user meta that will replace the actual usermeta informations if the modification is approved. I've looked at codex and I've discovered there is also the update_user_meta() function, it's not clear for me at the moment what can be the best choice to achive my scope. This is the code I have at the moment

            $user_id = $request->get_param('user_id');
            //TOFIX: mappatura meta input utente
            $customer = wp_update_user( 
                $user_id,
                array(
                    'user_email' => $request->get_param('email'),
                    'first_name' => $request->get_param('nome'),
                    'last_name' => $request->get_param('cognome'),
                    'user_login' => $request['user_login'],
                    //'display_name' => $request['nome'] .' '. $request['cognome'],
                    'rich_editing' => false,
                    'show_admin_bar_front' => false,
                    'role' => 'customer',
                    'meta_input' => array(
                        'indirizzo' => $request['indirizzo'],
                        'comune' => $request['comune'],
                        'provincia' => $request['provincia'],
                        'cap' => $request['cap'],
                        'nazione' => $request['nazione'],
                        'telefono_fisso' => $request['telefono_fisso'],
                        'telefono_cellulare' => $request['telefono_cellulare'],
                        'cod_fiscale_piva' => $request['cod_fiscale_piva'],
                        'codSDI' => $request['codSDI'],
                        'pec' => $request['pec'],
                        'num_tessera' => $request['num_tessera'],
                        'stato_account' => 'pending',
                    )
                )
            );

what I want to do is to add new temporary usermeta for the fields that users can modify so for example I want to have this kind of code

            $user_id = $request->get_param('user_id');
            //TOFIX: mappatura meta input utente
            $customer = wp_update_user( 
                $user_id,
                array(
                    'user_email' => $request->get_param('email'),
                    'first_name' => $request->get_param('nome'),
                    'last_name' => $request->get_param('cognome'),
                    'user_login' => $request['user_login'],
                    //'display_name' => $request['nome'] .' '. $request['cognome'],
                    'rich_editing' => false,
                    'show_admin_bar_front' => false,
                    'role' => 'customer',
                    'meta_input' => array(                        
                        'new_telefono_fisso' => $request['telefono_fisso'],
                        'new_telefono_cellulare' => $request['telefono_cellulare']
                    )
                )
            );

Basically the idea is to add the fields with the new_ prefix, so I can load them using the rest api and give a feedback on my vue front-end when the change occur and need to be approved. Any suggestion on what function or action I can use?